Ferromagnetically coupled magnetic recording media

ABSTRACT

A ferromagnetically coupled magnetic recording medium having a first ferromagnetic layer, a second ferromagnetic layer, and a ferromagnetic coupling layer to ferromagnetically couple the first ferromagnetic layer to the second ferromagnetic layer is used as stable magnetic media with high MrT in high density recording hard drives. The first ferromagnetic layer is the stabilization layer and the second ferromagnetic layer is the main recording layer. The ferromagnetic coupling layer comprises a conductive material having a thickness which produces ferromagnetic coupling between said first ferromagnetic layer and said second ferromagnetic layer via the RKKY interaction.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the field of disc drivestorage, and more particularly to ferromagnetically coupled magneticrecording media.

2. Description of the Related Art

Conventional disc drives are used to magnetically record, store andretrieve digital data. Data is recorded to and retrieved from one ormore discs that are rotated at more than one thousand revolutions perminute (rpm) by a motor. The data is recorded and retrieved from thediscs by an array of vertically aligned read/write head assemblies,which are controllably moved from data track to data track by anactuator assembly.

The three major components making up a conventional hard disc drive aremagnetic media, read/write head assemblies and motors. Magnetic media,which is used as a medium to magnetically store digital data, typicallyincludes a layered structure, of which at least one of the layers ismade of a magnetic material, such as CoCrPtB, having high coercivity andhigh remnant moment. The read/write head assemblies typically include aread sensor and a writing coil carried on an air bearing slider attachedto an actuator. This slider acts in a cooperative hydrodynamicrelationship with a thin layer of air dragged along by the spinningdiscs to fly the head assembly in a closely spaced relationship to thedisc surface. The actuator is used to move the heads from track to trackand is of the type usually referred to as a rotary voice coil actuator.A typical rotary voice coil actuator consists of a pivot shaft fixedlyattached to the disc drive housing closely adjacent to the outerdiameter of the discs. Motors, which are used to spin the magnetic mediaat rates of higher than 1,000 revolutions per minute (rpm), typicallyinclude brushless direct current (DC) motors. The structure of discdrives is well known.

Magnetic media can be locally magnetized by a read/write head, whichcreates a highly concentrated magnetic field that alternates directionbased upon bits of the information being stored. The highly concentratedlocalized magnetic field produced by the read/write head magnetizes thegrains of the magnetic media at that location, provided the magneticfield is greater than the coercivity of the magnetic media. The grainsretain a remnant magnetization after the magnetic field is removed,which points in the same direction of the magnetic field. A read/writehead that produces an electrical response to a magnetic signal can thenread the magnetization of the magnetic media.

Magnetic media structures are typically made to include a series of thinfilms deposited on top of aluminum substrates, ceramic substrates orglass substrates. FIG. 1 illustrates a conventionalanti-ferromagnetically coupled magnetic media structure having asubstrate 110, a seed layer 115, a first ferromagnetic layer 120, ananti-ferromagnetic coupling layer 125, a second ferromagnetic layer 130,and a protective overcoat 140.

Substrate 110 is typically made of Aluminum (Al), nickel-phosphorusplated aluminum, glass or ceramic. Seed layer 115 is typically made ofCr or a Cr alloy and can be less than 200 angstroms. First ferromagneticlayer 120 is the stabilization layer and can be made of a ferromagneticmaterial such as Co. Second ferromagnetic layer 130 is the mainrecording layer and is also made of a ferromagnetic material such as Co.Anti-ferromagnetic coupling (AFC) layer 125 is made of Ru and is used toanti-ferromagnetically couple the main recording layer with thestabilization layer.

In AFC media the main recording layer is anti-ferromagnetically coupledacross a Ru spacer layer with the thin magnetic stabilization layer. Thestability of the main recording layer increases because of the couplingwith the stabilization layer 120 and because of the decrease of thedemagnetization field that the main recording layer experiences. Thisincrease in stability of the main recording layer can be traded offagainst the decreasing average magnetic grain volume in the mainrecording layer. However, in this AFC structure the net MrT of thismedia is reduced (net MrT=(M_(r)T)_(ML)-(M_(r)T)_(SL)) causing anincrease in the effective electronic noise and a reduction in totalsignal-to-noise ratio (SNR) (total SNR=Media SNR+Electronic SNR).

The magnetic media structure of FIG. 1 lacks optimal magnetic propertiesbecause of high noise resulting from high magnetic exchange couplingbetween grains. Therefore what is needed is a magnetic media structurethat is useable for high-density recording, has a high MrT and isstable.

SUMMARY OF THE INVENTION

This limitation is overcome by using ferromagnetically coupled magneticrecording media instead of anti-ferromagnetically coupled magneticrecording media. A ferromagnetically coupled magnetic recording mediumcomprises a first ferromagnetic layer, a second ferromagnetic layer, anda ferromagnetic coupling layer to ferromagnetically couple the firstferromagnetic layer to the second ferromagnetic layer. The firstferromagnetic layer is the stabilization layer and the secondferromagnetic layer is the main recording layer. The ferromagneticcoupling layer comprises a conductive material having a thickness whichproduces ferromagnetic coupling between the first ferromagnetic layerand the second ferromagnetic layer via the RKKY interaction.

In one embodiment of the magnetic recording medium the conductivematerial of the ferromagnetic coupling layer can be Ru, Rh, Ir, Cr, Cu,Re, V or alloys made of these elements.

In another embodiment, the first ferromagnetic layer and the secondferromagnetic layer are made of Co-based alloys. Additionally theferromagnetic coupling layer is made of Ru and has a thickness rangewhich is between about 0 and 2 angstroms, or between about 11 angstromsand 17 angstroms, or between about 25 angstroms and 31 angstroms. Thisthickness range produces ferromagnetic coupling between the firstferromagnetic layer and the second ferromagnetic layer according to theRKKY interaction.

In another embodiment of the magnetic recording medium, theferromagnetic coupling layer includes a non-magnetic conductive layer,which is ferromagnetically polarized in the presence of the firstferromagnetic layer and the second ferromagnetic layer. In thisembodiment the ferromagnetic coupling layer has a thickness less than 6nanometers and can be made of Pt, Pd, Pt-alloys, or Pd-alloys.

In another embodiment of the magnetic recording medium, theferromagnetic coupling layer includes a weekly ferromagnetic layer thatprovides direct exchange interaction coupling between the firstferromagnetic layer and the second ferromagnetic layer. Theferromagnetic coupling layer can have a magnetization less than 300emu/cm³ and preferably has a magnetization less than 100 emu/cm³.Additionally, the ferromagnetic coupling layer can be made of Co, Ni, Feor alloys thereof.

In other embodiments of the invention, the first ferromagnetic layer andthe second ferromagnetic layer of the magnetic recording medium are madeof Co, Cr, or alloys containing Co or Cr. The alloys containing Co or Crcan have one or more of elements Pt, Ta, B, Mo, Ru, Si, Ge, Nb, Fe or Niadded to the alloy.

In other embodiments of the invention, the first ferromagnetic layer andthe second ferromagnetic layer of the magnetic recording medium are madeof Si, Al, Ti, Hf, W, Mg, Nb, Fe, B, V, Mn, Ge, Mo, Ru, Rh, Re, Pt, Zr,Y, Cr, Sm, Co, Ni or Ta. Some examples include TiO₂, Al₂O₃, MgO, WO₃,Cr₂O₃, Nb₂O₅, ZrO2, Ta2O5, MoO3, Y2O3, Sm2O3, CoO and CoCrPt+SiO₂.

Another embodiment of the invention includes a magnetic recordingmedium, comprising, a first ferromagnetic layer, a first interfacelayer, a ferromagnetic coupling layer, a second interface layer, asecond ferromagnetic layer, wherein the ferromagnetic coupling layer isused to ferromagnetically couple the first ferromagnetic layer and thesecond ferromagnetic layer. The first interface layer and the secondinterface layer can have magnetic moments with magnetic saturationsgreater than 300 emu/cm³ and preferably greater than 500 emu/cm³. Thefirst interface layer and the second interface layer can be made of Fe,Co or alloys made of Fe or Co. The alloys made of Fe or Co can be mixedwith one or more added elements which include Cr, Pt, Ta, B, Mo, Pd, Cu,Au, Ti, W, Ru, Si, Ge, Nb, or Ni.

Another embodiment of the invention includes a magnetic recordingmedium, comprising, a first ferromagnetic layer, a second ferromagneticlayer, a ferromagnetic coupling layer for ferromagnetically coupling thefirst ferromagnetic layer to the second ferromagnetic layer, wherein theferromagnetic coupling layer is anti-ferromagnetically coupled to boththe first ferromagnetic layer and the second ferromagnetic layer. Theferromagnetic coupling layer can further include two non-magnetic spacerlayers separated by a magnetic interface layer. The magnetic interfacelayer can include Fe, Co, FeX, or CoX where X is one or more of Cr, Pt,Ta, B, Mo, Ru, Si, Ge, Nb, or Ni. Additionally, the magnetic interfacelayer can have a magnetic saturation greater than 300 emu/cm³ andpreferably greater than 500 emu/cm³.

Another embodiment of the invention includes a magnetic recording mediumcomprising a first ferromagnetic structure further comprising a CoCrPtBlayer and a Co layer, a second ferromagnetic structure furthercomprising a Co layer and a CoCrPtB layer, and a ferromagnetic couplingstructure for ferromagnetically coupling the first ferromagnetic layerto the second ferromagnetic layer, wherein the ferromagnetic couplingstructure further comprises a first Ru layer, a Co layer, and a secondRu layer.

All of these embodiments can be implemented in both longitudinal andperpendicular magnetic recording medium. For example, other embodimentscan include the combinations of mixing a first ferromagnetic layer thatis perpendicular or longitudinal with a second ferromagnetic layer canalso be perpendicular or longitudinal.

All of these embodiments of the magnetic recording medium can be used ina hard disc drive, which comprises the magnetic recording mediumdescribed in the embodiments above, a motor for spinning the magneticrecording medium about its center and a transducer for reading andwriting on the magnetic recording medium while the magnetic recordingmedium is rotated about by the motor.

Other embodiments of the perpendicular magnetic media structure caninclude various thicknesses and compositions.

BRIEF DESCRIPTION OF THE INVENTION

FIG. 1 is a block diagram showing a prior art anti-ferromagneticallycoupled magnetic media structure.

FIG. 2A is a block diagram showing a ferromagnetically coupledlongitudinal magnetic media structure in accordance with one embodimentof the invention.

FIG. 2B is a block diagram showing a perpendicular magnetic mediastructure similar to the one shown in FIG. 2A in accordance with oneembodiment of the invention.

FIG. 3A is a block diagram showing a ferromagnetically coupledlongitudinal magnetic media structure having interface layers inaccordance with another embodiment of the invention.

FIG. 3B is a block diagram showing a perpendicular magnetic mediastructure similar to the one shown in FIG. 3A in accordance with oneembodiment of the invention.

FIG. 4A is a block diagram showing a ferromagnetically coupledlongitudinal magnetic media structure having interface layers inaccordance with another embodiment of the invention.

FIG. 4B is a schematic drawing showing a ferromagnetically coupledlongitudinal magnetic media structure with magnetic grains in theinterface layer in accordance with another embodiment of the invention.

FIG. 4C is a schematic drawing showing a ferromagnetically coupledlongitudinal magnetic media structure with canted magnetic grains in theinterface layer in accordance with another embodiment of the invention.

FIG. 5A-5C are illustrations showing perpendicular multilayer magneticmedia structures similar to the ones shown in FIG. 4A-4C.

FIG. 6-7 are graphs showing vibrating sample magnetometer (VSM) data forsamples having different thickness of magnetic layers containing cobalt(Co).

FIG. 8 is a block diagram showing a hard drive using the magneticrecording media described with reference to FIG. 2A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention provides a system and method for high a real densitymagnetic recording which includes a magnetic media structure that has ahigh MrT while still being stable:

FIG. 2A illustrates a multilayer magnetic media structure 200 having aferromagnetic coupling layer used to make stable media with high MrT, inaccordance with one embodiment of the invention. Magnetic mediastructure 200 includes a substrate 210, a seed layer and or under layersubstructure 215 including one or more layers, a first ferromagneticlayer 220, a ferromagnetic coupling layer 225, a second ferromagneticlayer 230, a magnetic written bit boundary 235 and a protective overcoat240.

Substrate 210 of magnetic media structure 200 is a non-magnetic materialsufficiently thick to provide sufficient rigidity. Substrate 210 can bemade out of Aluminum (Al), nickel-phosphorus plated aluminum, Al—Mgbased alloys, other aluminum based alloys, other non-magnetic metals,other non-magnetic alloys, glass, ceramic, polymers, glass-ceramics,chemically treated glass, and composites and/or laminates thereof. Theseed layer and or under layer substructure 215 can vary depending on thetype of magnetic media 200. For example, if the magnetic media 200 islongitudinal media then the seed layer and or under layer substructure215 includes non-magnetic seed and under layers capable of controllingthe crystallographic texture of cobalt based alloys. More specifically,the seed layers may include amorphous or fine grain material such asNiAl, NiP, CoW, CrTa, or CrTi. The under layers may include Cr-basedalloys. However, if the magnetic media 200 is perpendicular media thenthe seed layer and or under layer substructure 215 can include cohesivelayers, soft magnetic underlayers and interlayers. Specifically, thecohesive layer can include Ti, Cr, CrTa, or Ta, and the soft magneticunderlayers can include Fe or Co rich magnetic layers whereas theinterlayer structure could consist of at least one amorphous layer suchas Ta, TaCr, TiCr, or/and face-centered-cubic (FCC) layer such as Cu,Ag, Au, Pt and hexagonal-closed-packed (HCP) layer such as Ru, Realloys.

First ferromagnetic layer 220 and second ferromagnetic layer 230 aremagnetic materials exhibiting ferromagnetic properties. Firstferromagnetic layer refers to the ferromagnetic layer closer to thesubstrate and is a stabilization layer whereas second ferromagneticlayer refers to the ferromagnetic layer further away from the substrateand is a main recording layer. Therefore, throughout this specificationthe terms first ferromagnetic layer 220 and second ferromagnetic layer230 may be interchanged with stabilization layer and main recordinglayer, respectively. Each of the stabilization layer and main recordinglayer can exhibit ferromagnetic or superparamagnetic properties whilethe entire magnetic media structure 200 exhibits ferromagneticproperties. First ferromagnetic layer 220 and second ferromagnetic layer230 can be a single layer or a multi-layered ferromagnetic structure.Some examples of first ferromagnetic layer 220 and second ferromagneticlayer 230 are alloys containing Co, Cr, or CoCr. These alloys containingCo, Cr or CoCr can further have elements selected from the group Pt, Ta,B, Mo, Ru, Si, Ge, Nb, Fe and Ni added in. Other examples of firstferromagnetic layer 220 and second ferromagnetic layer 230 includealloys containing at least one oxide material selected from the groupconsisting of Si, Al, Ti, Hf, W, Mg, Nb, Fe, B, V, Mn, Ge, Mo, Ru, Rh,Re, Pt, Zr, Y, Cr, Sm, Co, Ni and Ta. Some example of an alloycontaining an oxide are TiO₂, Al₂O₃, MgO, WO₃, Cr₂O₃, Nb₂O₅, ZrO2,Ta2O5, MoO3, Y2O3, Sm2O3, CoO, and CoCrPt+SiO₂.

The ferromagnetic coupling layer 225, which ferromagnetically couplesthe first ferromagnetic layer 220 and the second ferromagnetic layer 230can be a non-magnetic conductive layer that provides RKKY coupling, anon-magnetic conductive layer that is ferromagnetically polarized in thepresence of the first ferromagnetic layer 220 and the secondferromagnetic layer 230, or a weekly ferromagnetic layer that providesdirect exchange interaction coupling. Although FIG. 2A shows thatferromagnetic coupling layer 225 is a single layer, ferromagneticcoupling layer 225 can include multiple layers as further discussed withreference to the examples FIGS. 3 and 4 below.

Ferromagnetic coupling via non-magnetic conductive layer that providesRKKY coupling can be achieved if the ferromagnetic coupling layer 225falls within specific thickness ranges. Some examples of materials usedfor RKKY coupling include Ru, Rh, Ir, Cr, Cu, Re, V as well as alloysmade of these elements. For example if the RKKY coupling layer is Ru andthe ferromagnetic layers are Co-based alloys then the ferromagneticcoupling can be achieved for Ru thicknesses ranging between 0 to 2angstroms, and from about 11 angstroms to 17 angstroms, and from about25 angstroms to 31 angstroms.

Ferromagnetic coupling via a non-magnetic conductive layer that isferromagnetically polarized in the presence of the first ferromagneticlayer 220 and the second ferromagnetic layer 230 can be achieved with aferromagnetic coupling layer 225 made of specific materials. Someexamples of materials that are suitable for use as a ferromagneticcoupling layer 235 include Pt, Pd, and alloys thereof which areferromagnetically polarized when in the presence of a ferromagneticlayer, independent of thickness when the thickness is less than 6 nm.

Ferromagnetic coupling via a weekly ferromagnetic layer that providesdirect exchange interaction coupling can be achieved with aferromagnetic coupling layer 225 made of specific materials. Someexamples of materials include Co, Ni, Fe and alloys thereof having amagnetization less than 300 emu/cm³ and preferably less than 100emu/cm³.

Magnetic written bit boundary 235 is a schematic demarcation whichseparates magnetic bits aligned in one direction from magnetic bitsaligned in another direction. The position of the magnetic written bitboundary is determined by the writing head, which writes in a specificarea depending on the design of the magnetic media and the magnetichead. Protective overcoat 240 is a protective layer deposited onto overthe magnetic recording stack to protect it both during the manufactureof the hard drive or during operation of the hard drive. Protectiveovercoat 240 can be a carbon containing layer such asdiamond-like-carbon which is sputtered onto the second ferromagneticlayer 230. The thickness of protective overcoat 240 can be less than 50angstroms and is preferably less than 30 angstroms.

The magnetic media structure of FIG. 2A shows first ferromagnetic layer220 and second ferromagnetic layer 230 are ferromagnetically coupledtogether through ferromagnetic coupling layer 225. The arrows shown infirst ferromagnetic layer 220 and second ferromagnetic layer 230represent the direction in which the magnetic written bits within theselayers are magnetized. The arrows represent the direction of themagnetic written bit moments in the absence of a magnetic field, whichis also referred to as the remnant moment. The right magnetic writtenbits in both first ferromagnetic layer 220 and second ferromagneticlayer 230 are coupled together ferromagnetically pointing in the samedirection towards the left of the FIG. 2A. Similarly, the left magneticwritten bits in both first ferromagnetic layer 220 and secondferromagnetic layer 230 are coupled together ferromagnetically pointingin the same direction towards the right of the FIG. 2A.

The magnetic media structure described with reference to FIG. 2A aboveis made using magnetic media manufacturing processes well known in theart. Conventional media manufacturing processes include texturingsubstrate 210, cleaning substrate 210, and depositing layers 215 through240. The deposition process includes sputtering target material ofusually the same material as their respective layers so that thin filmsof the sputtered material grow on the substrate. The deposition processis usually done at ambient temperatures and only after the depositionchamber has been evacuated to low pressures.

The magnetic layers of the alloy perpendicular or longitudinal recordingmedia, which include a single or a couple of magnetic layers wherein thethickness of each layer can range from one atomic layer (monolayer) tothicknesses of about several hundred angstroms, are typically depositedonto cold substrates or substrates that have been heated to hightemperatures, such as 250° C.

FIG. 2B illustrates a perpendicular multilayer magnetic media structuresimilar to the one shown in FIG. 2A except that it shows perpendicularrecording as oppose to longitudinal recording. In FIG. 2A the magneticdomains found within first ferromagnetic layer 220 and secondferromagnetic layer 220 are aligned parallel to the substrate 210 andlongitudinal to the plane of the film whereas in FIG. 2B the magneticdomains of first ferromagnetic layer 220 and second ferromagnetic layer220 are aligned perpendicular to the substrate 210 and perpendicular tothe plane of the film. The magnetic media structure of FIG. 2B showsfirst ferromagnetic layer 220 and second ferromagnetic layer 230 areferromagnetically coupled together through ferromagnetic coupling layer225. The arrows shown in first ferromagnetic layer 220 and secondferromagnetic layer 230 represent the direction in which the magneticwritten bits within these layers are magnetized in the absence of anexternal magnetic field. The right magnetic written bits in both firstferromagnetic layer 220 and second ferromagnetic layer 230 are coupledtogether ferromagnetically pointing in the same direction towards thesubstrate 210. Similarly, the left magnetic written bits in both firstferromagnetic layer 220 and second ferromagnetic layer 230 are coupledtogether ferromagnetically pointing in the same direction away from thesubstrate 210.

FIG. 3A illustrates another magnetic media structure 300 having aferromagnetic coupling layer in accordance with another embodiment ofthe invention. Magnetic media structure 300 includes a substrate 210, aseed layer and or under layer substructure 215 including one or morelayers, a first ferromagnetic layer 220, a first interface layer 310, aferromagnetic coupling layer 225, a second interface layer 315, a secondferromagnetic layer 230, a magnetic written bit boundary 235, and aprotective overcoat 240. In magnetic media structure 300 there is aninterface layer between the first ferromagnetic layer 220 and theferromagnetic coupling layer 225 as well as between the secondferromagnetic layer 230 and the ferromagnetic coupling layer 225. Firstinterface layer 310 and the second interface layer 315 can be made ofmaterials having large magnetic moments with magnetic saturationsgreater than 300 emu/cm³ (M_(s)>300 emu/cm³) and preferably greater than500 emu/cm³ (M_(s)>500 emu/cm³). Some examples of materials that can beused for first interface layer 310 and second interface layer 315include materials having high moment elements such as Fe or Co or alloysmade of Fe or Co mixed with one or more added elements including Cr, Pt,Ta, B, Mo, Pd, Cu, Au, Ti, W, Ru, Si, Ge, Nb, or Ni.

FIG. 3B illustrates a perpendicular multilayer magnetic media structuresimilar to the one shown in FIG. 3A except that it shows perpendicularrecording as oppose to longitudinal recording. In FIG. 3A the magneticdomains found within first ferromagnetic layer 220, second ferromagneticlayer 230, first interface layer 310, and second interface layer 315 arealigned parallel to the substrate 210 and longitudinal to the plane ofthe film whereas in FIG. 3B the magnetic domains of first ferromagneticlayer 220, second ferromagnetic layer 230, first interface layer 310,and second interface layer 315 are aligned perpendicular to thesubstrate 210 and perpendicular to the plane of the film. The magneticmedia structure of FIG. 3B shows first ferromagnetic layer 220 andsecond ferromagnetic layer 230 are ferromagnetically coupled togetherthrough first interface layer 310, second interface layer 315, andspacer layer 330. The arrows shown in first ferromagnetic layer 220 andsecond ferromagnetic layer 230 represent the direction in which themagnetic written bits within these layers are magnetized in the absenceof an external magnetic field. The right magnetic written bits in bothfirst ferromagnetic layer 220 and second ferromagnetic layer 230 arecoupled together ferromagnetically pointing in the same direction towardthe substrate 210. Similarly, the left magnetic written bits in bothfirst ferromagnetic layer 220 and second ferromagnetic layer 230 arecoupled together ferromagnetically pointing in the same direction awayfrom the substrate 210.

FIG. 4A-4C illustrate three other longitudinal magnetic media structureshaving ferromagnetic coupling in accordance with other embodiments ofthe invention. In the embodiments of FIG. 4A-4C, the two ferromagneticlayers are ferromagnetically coupled indirectly by twoanti-ferromagnetically coupled layers. The ferromagnetic couplingsection can be a) two non-magnetic spacer layers separated by a magneticinterface layer as further discussed with reference to FIG. 4A, or b) anon-magnetic spacer layer with a magnetic grain structure located in themiddle of the layer as further discussed with reference to FIG. 4B, orc) a non-magnetic spacer layer with magnetic grains substantiallyuniformly distributed across a non-magnetic spacer layer as furtherdiscussed with reference to FIG. 4C. In the three embodiments of FIG.4A-4C, the interaction between the first ferromagnetic layer and secondferromagnetic layer is provided via RKKY coupling across theferromagnetic coupling layer.

FIG. 4A is a block diagram showing a ferromagnetically coupledlongitudinal magnetic media structure having interface layers inaccordance with an embodiment of the invention. FIG. 4A shows a firstferromagnetic layer 220, a second ferromagnetic layer 230 and aferromagnetic coupling layer which further includes an interface layer410, a first spacer layer 415, and a second spacer layer 420. Interfacelayer 410 can be made of materials having large magnetic moments withmagnetic saturations greater than 300 emu/cm³ (M_(s)>300 emu/cm³) andpreferably greater than 500 emu/cm³ (M_(s)>500 emu/cm³). Some examplesof materials that can be used for interface layer 410 include materialshaving high moment elements such as Fe or Co or alloys made of Fe or Comixed with one or more added elements including Cr, Pt, Ta, B, Mo, Ru,Si, Ge, Nb, or Ni. Additionally, interface layer 410 can be a continuousfilm or discontinuous film depending on the material used or theconditions used to deposit the film. First spacer layer 415 and a secondspacer layer 420 can generally consist of most non-magnetic material orcomposition. Some specific examples of materials useable for firstspacer layer 415 and second spacer layer 420 include Ru, Rh, Ir, Cr, Cu,Re, V and alloys made of these elements. The thickness of first spacerlayer 415 and second spacer layer 420 are chosen to maximizeanti-ferromagnetic coupling between the magnetic interface layer 410 andboth first ferromagnetic layer 220 and second ferromagnetic layer 230.The thickness of first spacer layer 415 and second spacer layer 420ranges from 4 to 10 angstroms, which is approximately 2-3 monolayers.

FIG. 4B is a schematic drawing showing a ferromagnetically coupledlongitudinal magnetic media structure with magnetic grains in theinterface layer in accordance with another embodiment of the invention.Some examples of materials that can be used for magnetic grains in theinterface layer 225 include materials having high moment elements suchas Fe or Co or alloys made of Fe or Co mixed with one or more addedelements including Cr, Pt, Ta, B, Mo, Ru, Si, Ge, Nb, or Ni.

FIG. 4C is a schematic drawing showing a ferromagnetically coupledlongitudinal magnetic media structure with canted magnetic grains in theinterface layer in accordance with another embodiment of the invention.Some examples of materials that can be used for magnetic grains in theinterface layer 225 include materials having high moment elements suchas Fe or Co or alloys made of Fe or Co mixed with one or more addedelements including Cr, Pt, Ta, B, Mo, Ru, Si, Ge, Nb or Ni.

FIG. 5A-5C illustrate perpendicular multilayer magnetic media structuressimilar to the ones shown in FIG. 4A-4C with the exception that theseshow perpendicular recording as oppose to longitudinal recording. InFIG. 4A-4C the magnetic domains found within first ferromagnetic layer220, second ferromagnetic layer 230 and the interface layer 410 arealigned parallel to the substrate 210 and longitudinal to the plane ofthe film whereas in FIG. 5A-5C the magnetic domains of firstferromagnetic layer 220, second ferromagnetic layer 230, and theinterface layer 410 are aligned perpendicular to the substrate 210 andperpendicular to the plane of the film. The magnetic media embodimentsillustrated in FIG. 5A-5C show the first ferromagnetic layer 220 and thesecond ferromagnetic layer 230 ferromagnetically coupled togetherthrough the interface layer 410. The arrows shown in first ferromagneticlayer 220 and second ferromagnetic layer 230 represent the direction inwhich the magnetic written bits within these layers are magnetized inthe absence of an external magnetic field. The right magnetic writtenbits in both first ferromagnetic layer 220 and second ferromagneticlayer 230 are coupled together ferromagnetically pointing in the samedirection toward the substrate 210. Similarly, the left magnetic writtenbits in both first ferromagnetic layer 220 and second ferromagneticlayer 230 are coupled together ferromagnetically pointing in the samedirection away from the substrate 210.

In addition to magnetic media structures with first ferromagnetic layer220 and second ferromagnetic layer 230 having the same magneticorientation, as described above with reference to FIG. 2-5C, othercombinations are possible. Other combinations include a mixture of afirst ferromagnetic layer that is perpendicular or longitudinal with asecond ferromagnetic layer can also be perpendicular or longitudinal.The first of these combinations is a magnetic recording medium having afirst ferromagnetic layer, a second ferromagnetic layer, and aferromagnetic coupling layer to ferromagnetically couple the firstferromagnetic layer to the second ferromagnetic layer wherein themagnetocrystalline anisotropy of the first and second ferromagneticlayers are perpendicular to the film plane. The second of thesecombinations is a magnetic recording medium having a first ferromagneticlayer, a second ferromagnetic layer, and a ferromagnetic coupling layerto ferromagnetically couple the first ferromagnetic layer to the secondferromagnetic layer wherein the magnetocrystalline anisotropy of thefirst and second ferromagnetic layers are parallel to the film plane.The third of these combinations is a magnetic recording medium having afirst ferromagnetic layer, a second ferromagnetic layer, and aferromagnetic coupling layer to ferromagnetically couple the firstferromagnetic layer to the second ferromagnetic layer wherein themagnetocrystalline anisotropy of the first ferromagnetic layer isperpendicular to the film plane and the magnetocrystalline anisotropy ofthe second ferromagnetic layer is parallel to the film plane. The fourthof these combinations is a magnetic recording medium having a firstferromagnetic layer, a second ferromagnetic layer, and a ferromagneticcoupling layer to ferromagnetically couple the first ferromagnetic layerto the second ferromagnetic layer, wherein the magnetocrystallineanisotropy of the first ferromagnetic layer is parallel to the filmplane and the magnetocrystalline anisotropy of the second ferromagneticlayer is perpendicular to the film plane.

FIG. 6 is a graph showing vibrating sample magnetometer (VSM) data forsamples having different thickness of magnetic layers containing cobalt(Co) made in accordance with an embodiment of this invention. FIG. 6data is for a magnetic media structure sputtered on Al/NiP substrateshaving a Cr underlayer, a paramagnetic hexagonal intermediate layer, aCoCr magnetic layer, CoCrPtB magnetic layers, Co interface layers, and aRu/Co/Ru ferromagnetically coupled (FC) layer. Specifically the magneticmedia structure of FIG. 6 isCr/CoCr/CoCrPtB/Co/Ru/Co(varied)/Ru/Co/CoCrPtB. The thickness of Ruspacer layers is about 0.6 nm and is chosen to achieve maximumanti-ferromagnetic coupling between CoCrPtB/Co and the Co that islocated in-between Ru spacer layers and is labeled as Co(varied) in theabove structure. A 35 Å overcoat was applied using magnetron sputteringto protect the films from corrosion.

FIG. 6 and 7 data shows that when the thickness of the Co layer in theRu/Co/Ru ferromagnetic coupling layer increases, the coercivity of themagnetic media structure decreases. Additionally, the data shows thatwhen the Co layer thickness in the Ru/Co/Ru ferromagnetic coupling layeris larger than 0.15 nm, the coupling constant J_(r) first increases thendecreases.

For simplicity the CoCrPtB/Co layers located between the CoCr₃₇ and Rulayers will be labeled as bottom layers (BL) and the Co/CoCrPtB layersthat are located above Ru will be labeled as top layers (TL), in theCr/CoCr37/CoCrPtB/Co/Ru/Co(varied)/Ru/Co/CoCrPtB structure. When theapplied magnetic field is zero, both TL and BL point in the samedirection if the ferromagnetic coupling is large enough to overcome themagnetostatic interaction between TL and BL. If the applied externalmagnetic field is larger than the exchange field, due to theferromagnetic coupling between magnetic layers, then the BL will orientin the direction of the applied external magnetic field. Since TLexperiences both the applied external magnetic field and the field dueto the interaction with the BL, there is a reduction in the coercivityfield of the TL.

FIG. 6 and 7 data also shows that when the Co layer thickness in theRu/Co/Ru ferromagnetic coupling layer is less than 0.15 nm (Co<0.15 nm),the strength of the ferromagnetic interaction is similar to the strengthof the magnetostatic interaction. When the thickness of the Co layer isapproximately 0.7 nm, the ferromagnetic interaction is strong enough toovercome the magnetostatic interaction and orient TL and BL parallel ata zero applied external magnetic field.

There are several differences between anti-ferromagnetically coupled(AFC) media and ferromagnetically coupled (FC) media. In order tocompare and contrast AFC media and FC media, AFC and FC media having thesubstantially the same MrT are compared. The coupling strength betweenthe magnetic layers in AFC and FC media is substantially similar. Thestability of the main recording layer, which is the second ferromagneticlayer 230, in both the AFC and FC media increases as a result of thecoupling with the stabilization layer, which is the first ferromagneticlayer 220. The increase in stability depends on the coupling strengthbetween main recording layer 230 and the stabilization layer 220. Onedifference between AFC media and FC media, which makes AFC mediaadvantages, is that the remanent coercivity of the AFC media increasesas a result of the coupling while the remanent coercivity of the FCmedia decreases as a result of the coupling. Another difference is thatAFC media has a better switching field distribution (SFD) than FC media.

There are also several differences between conventional media, which isnot AFC, and ferromagnetically coupled (FC) media. In order to compareand contrast conventional media and FC media, conventional and FC mediahaving substantially the same MrT are compared. The remanent coercivityof the of the main recording layer in FC media can be reduced viacoupling whereas conventional media does not have this advantage.Another difference is that the main recording layer in FC media isthinner than it is in conventional media, which is an advantage if thewriting bubble in BL is significantly bigger than in the main recordinglayer.

FIG. 8 is an exploded perspective view of a magnetic hard drive, whichuses a magnetic recording media made using a substrate made inaccordance with an embodiment of this invention. The magnetic hard drive800, illustrated in FIG. 8, includes a housing 805 further having a base810 sealed to a cover 815 by a seal 820. The hard drive 800 alsoincludes a spindle 830 to which is attached one or more magneticrecording media 200 having surfaces 840 covered with a magneticrecording media (not shown) for magnetically storing information.Although FIG. 8 illustrates a hard drive 800 using several magneticrecording media 200, only one surface is required to make the hard drive800 operational. A spindle motor (not shown in this figure) rotates theplurality of magnetic recording media 200 past read/write heads 845 thatare suspended above surfaces 840 of the magnetic recording media 200 bya suspension arm assembly 850. Under normal operating conditions, thespindle motor rotates the magnetic recording media 200 at high speedspast the read/write heads 845 while the suspension arm assembly 850moves and positions the read/write heads over one of several radiallyspaced tracks (not shown). This allows the read/write heads 845 to readand write magnetically encoded information to the surfaces 840 of themagnetic recording media 200 at selected locations.

It will also be recognized by those skilled in the art that, while theinvention has been described above in terms of preferred embodiments, itis not limited thereto. Various features and aspects of theabove-described invention may be used individually or jointly. Further,although the invention has been described in the context of itsimplementation in a particular environment and for particularapplications, those skilled in the art will recognize that itsusefulness is not limited thereto and that the present invention can beutilized in any number of environments and implementations.

1. A magnetic recording medium, comprising; a first ferromagnetic layer;a second ferromagnetic layer; and a ferromagnetic coupling layer toferromagnetically couple said first ferromagnetic layer to said secondferromagnetic layer.
 2. The magnetic recording medium of claim 1 whereinsaid ferromagnetic coupling layer further comprises: a conductivematerial a thickness which produces ferromagnetic coupling between saidfirst ferromagnetic layer and said second ferromagnetic layer via theRKKY interaction.
 3. The magnetic recording medium of claim 2 whereinsaid conductive material is selected from the group consisting of Ru,Rh, Ir, Cr, Cu, Re, V, and alloys made of these elements.
 4. Themagnetic recording medium of claim 1: wherein said first ferromagneticlayers is made of a Co-based alloy; wherein said second ferromagneticlayer is made of a Co-based alloy; and wherein said ferromagneticcoupling layer is Ru and has a thickness range selected from the groupcomprising of 0 to 2 angstroms, 11 angstroms to 17 angstroms, and 25angstroms to 31 angstroms.
 5. The magnetic recording medium of claim 1wherein said ferromagnetic coupling layer further comprises anon-magnetic conductive layer that is ferromagnetically polarized in thepresence of said first ferromagnetic layer and said second ferromagneticlayer.
 6. The magnetic recording medium of claim 5 wherein saidferromagnetic coupling layer is made of a material selected from thegroup consisting of Pt, Pd, Pt-alloys, and Pd-alloys.
 7. The magneticrecording medium of claim 6 wherein said ferromagnetic coupling layerhas a thickness less than 6 nanometers.
 8. The magnetic recording mediumof claim 1 wherein said ferromagnetic coupling layer further comprises aweekly ferromagnetic layer that provides direct exchange interactioncoupling between said first ferromagnetic layer and said secondferromagnetic layer.
 9. The magnetic recording medium of claim 8 whereinsaid ferromagnetic coupling layer is made of a material selected fromthe group consisting of Co, Ni, Fe and alloys thereof.
 10. The magneticrecording medium of claim 8 wherein said ferromagnetic coupling layerhas a magnetization less than 300 emu/cm³.
 11. The magnetic recordingmedium of claim 1 wherein said first ferromagnetic layer and said secondferromagnetic layer are selected from the group consisting of alloyscontaining Co and Cr, and alloys containing CoCr with one or more addedelements selected from the group consisting of Pt, Ta, B, Mo, Ru, Si,Ge, Nb, Fe and Ni.
 12. The magnetic recording medium of claim 1 whereinsaid first ferromagnetic layer has a magnetocrystalline anisotropyperpendicular to a film plane and said second ferromagnetic layer has amagnetocrystalline anisotropy perpendicular to a film plane.
 13. Themagnetic recording medium of claim 1 wherein said first ferromagneticlayer has a magnetocrystalline anisotropy parallel to a film plane andsaid second ferromagnetic layer has a magnetocrystalline anisotropyparallel to a film plane.
 14. The magnetic recording medium of claim 1wherein said first ferromagnetic layer has a magnetocrystallineanisotropy parallel to a film plane and said second ferromagnetic layerhas a magnetocrystalline anisotropy perpendicular to a film plane. 15.The magnetic recording medium of claim 1 wherein said firstferromagnetic layer has a magnetocrystalline anisotropy perpendicular toa film plane and said second ferromagnetic layer has amagnetocrystalline anisotropy parallel to a film plane.
 16. The magneticrecording medium of claim 13 wherein said first ferromagnetic layer andsaid second ferromagnetic layer comprises at least one oxide material,said oxide material further comprising an element selected from thegroup consisting of Si, Al, Ti, Hf, W, Mg, Nb, Fe, B, V, Mn, Ge, Mo, Ru,Rh, Re, Pt, Zr, Y, Cr, Sm, Co, Ni and Ta.
 17. The magnetic recordingmedium of claim 13 wherein said first ferromagnetic layer and saidsecond ferromagnetic layer comprises CoCrPt and at least one compoundselected from the group consisting of TiO₂, Al₂O₃, MgO, WO₃, Cr₂O₃,Nb₂O₅, ZrO₂, Ta₂O₅, MoO₃, Y₂O₃, Sm₂O₃, CoO, and SiO₂.
 18. A magneticrecording medium, comprising; a first ferromagnetic layer; a firstinterface layer; a ferromagnetic coupling layer; a second interfacelayer; a second ferromagnetic layer; and wherein said ferromagneticcoupling layer is used to ferromagnetically couple said firstferromagnetic layer and said second ferromagnetic layer.
 19. Themagnetic recording medium of claim 18 wherein said first interface layerand said second interface layer have magnetic moments with magneticsaturations greater than 300 emu/cm³.
 20. The magnetic recording mediumof claim 18 wherein said first interface layer and said second interfacelayer are made from a material selected from the group consisting of Fe,Co and alloys made of Fe or Co mixed with one or more added elementsselected from the group consisting of Cr, Pt, Ta, B, Mo, Pd, Cu, Au, Ti,W, Ru, Si, Ge, Nb, and Ni.
 21. A magnetic recording medium, comprising;a first ferromagnetic layer; a second ferromagnetic layer aferromagnetic coupling layer for ferromagnetically coupling said firstferromagnetic layer to said second ferromagnetic layer; and wherein saidferromagnetic coupling layer is anti-ferromagnetically coupled to bothsaid first ferromagnetic layer and said second ferromagnetic layer. 22.The magnetic recording medium of claim 21 wherein said ferromagneticcoupling layer further comprises two non-magnetic spacer layersseparated by a magnetic interface layer.
 23. The magnetic recordingmedium of claim 22 wherein said magnetic interface layer comprises amaterial selected from the group consisting of Fe, Co, FeX, and CoX,wherein said X is one or more of Cr, Pt, Ta, B, Mo, Ru, Si, Ge, Nb, andNi.
 24. The magnetic recording medium of claim 22 wherein said magneticinterface layer has a magnetic saturations greater than 300 emu/cm³. 25.A magnetic recording medium, comprising; a first ferromagnetic structurefurther comprising a CoCrPtB layer and Co layer; a second ferromagneticstructure further comprising a Co layer and a CoCrPtB layer; and aferromagnetic coupling structure for ferromagnetically coupling saidfirst ferromagnetic layer to said second ferromagnetic layer, saidferromagnetic coupling structure further comprising a first Ru layer, aCo layer, and a second Ru layer.
 26. A disc drive, comprising: amagnetic recording media including a protective overcoat layer; a motorfor spinning said magnetic media about its center; a transducer forreading and writing on said magnetic media while said magnetic media isrotated about by said motor; and wherein said magnetic recording mediafurther comprising: a first ferromagnetic layer; a second ferromagneticlayer; and a ferromagnetic coupling layer to ferromagnetically couplesaid first ferromagnetic layer to said second ferromagnetic layer.